In some conventional electric drive apparatuses, which are used for an electric power steering system for assisting steering operation of a driver, an electronic control unit is combined with a motor. The control unit for the electric drive apparatus is required to be compact in size, low in noise and effective to increase output torque of the motor.
According to the following patent documents 1 and 2, three capacitors, which smooth variation in voltage of an input power source, are arranged in as row. In addition, six power modules are located in parallel in two rows. The row of three capacitors and the rows of six power modules are arranged in an L-shape. Current supplied from the power source flows from first bus bars to the power modules through the capacitors and second bus bars.    (Patent document 1) JP 3729176    (Patent document 2) JP 2004-215335A
However, the control unit needs be sized large if the capacitors and the power modules are arranged in L-shape. The first bus bars, which connect the capacitors and the power modules, increase impedance of electric conductor and lower performance of the capacitors. If the impedance of electric conductor increases, the current supplied from the power source to the motor through the control unit decreases and the output torque of the motor decreases.